This invention relates to a liquid or beverage dispensing device which is intended for use in a motor vehicle.
Numerous attempts have heretofore been made to produce a liquid dispenser for a motor vehicle which is capable of preparing a hot beverage, a cold beverage, or both. Most of these devices include a number of impractical features which adversely affect the cost, safety or versatility of the dispenser.
Many of these devices provided for the installation of the liquid storage tank in the engine compartment rather than in the passenger compartment. In addition to the sanitary considerations associated with such an installation, there is the problem that the liquid in the line from the tank to the dispensing head cools and must therefore generally be constantly recirculated to maintain adequate temperature.
Many liquid dispensers utilize a vacuum pumping system operating in conjunction with the vehicle's engine. This requires complex, costly valving systems and raises the possibility that an engine back-fire would be directed into the passenger compartment.
Other liquid dispensers heat the liquid with gases from the engine exhaust manifold. This is a difficult source of heat to deal with and the gas-liquid heat exchanger creates many problems due to the high temperature differential involved and the toxicity of the gases.
Another approach which has been frequently taken heretofore involves heating the liquid in the storage tank by electrical power obtained from the vehicle's electrical system. This approach severely limits the amount of water which can be heated, especially in a short time period.
Another drawback of the motor vehicle liquid dispensing devices used heretofore is the absence of automatic means of notifying the occupant of the vehicle that the liquid has reached the proper dispensing temperature and also of preventing the operation of the dispensing means until the liquid has reached that temperature. The absence of such features means that the vehicle's occupant cannot know whether the liquid has been properly heated until after it is in his cup.
The devices used heretofore have also failed to provide means to prevent the liquid from falling below a level that would expose the heating element located in the liquid storage tank. Without such a preventive means, there is a high probability of oxidation of the heating element which would shorten the useful life of the liquid dispensing device and add undesirable contaminants to the liquid supply.